ERP Implementation Timeline: What to Expect Week by Week

The most common fear about ERP implementation is the horror story: 18 months, three times over budget, still not working. These stories are real — but they almost always involve enterprise ERP projects with consultants, not focused custom builds for manufacturing SMBs.

Here is a realistic week-by-week timeline for a custom ERP covering 4–5 core modules for a manufacturing or trading company.

Weeks 1–2: Discovery and Workflow Mapping

This is the most important phase. Your vendor maps every workflow your team currently follows: how stock is received, how production jobs are created, how orders come in, how dispatch is coordinated. Good discovery prevents 80% of the "but I thought it would do X" complaints at go-live.

Your team's role: make key people available for 4–6 hours of discovery interviews. Bring your actual Excel files and process documents.

Week 3: Scope Document and Approval

Your vendor delivers a scope document: every module, every feature, every screen — and what is explicitly excluded. You review it, raise questions, and approve it. This document is the contract. Changes after this point cost extra — that is fair and expected.

Weeks 4–8: Development With Weekly Demos

Development happens in 1–2 week sprints. At the end of each sprint you see a working demo of what was built. You can give feedback, test workflows, and flag issues early — not at the end when everything is baked in.

This is where most of your feedback input happens. Plan to spend 2–3 hours per week reviewing demos and testing key workflows with your operations team.

Week 9: User Acceptance Testing

Your team runs the system against real scenarios: GRN a real purchase order, create a real production job, dispatch a real delivery. Any workflow gaps are identified here and fixed before go-live. Budget 2–3 days for your key users.

Week 10: Data Migration and Training

Historical data — item master, customer list, opening stock, vendor list — is cleaned and imported. Key users are trained on their role in the system. Training typically takes 4–8 hours per role.

Week 11: Go-Live

You switch to the ERP for live operations. For the first 1–2 weeks, run parallel with your old Excel system if needed — this removes risk without delaying the transition. Your vendor is available for same-day support during this period.

Weeks 12–22: Post-Launch Support

Minor issues, workflow tweaks, and user questions handled by your vendor. The first 3 months post-launch are included in the project cost. After that, an optional monthly support retainer covers ongoing changes.

What Causes Delays

Slow decisions on scope: if approvals take 2 weeks instead of 2 days, the project slips
Key stakeholder unavailability during discovery: the store manager is always traveling
Data migration complexity: Excel files with years of inconsistent formatting take time to clean
Scope creep: adding requirements after the scope is approved
Testing bottlenecks: UAT assigned to someone who cannot free up time from operations